linux-kernel - Re: [PATCH v2 2/2] staging: ion: chunk_heap: use %pad for printing dma_addr

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Date:	Mon, 04 May 2015 22:59:39 -0700
From:	Mitchel Humpherys <mitchelh@...eaurora.org>
To:	Colin Cross <ccross@...roid.com>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	devel@...uxdriverproject.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	John Stultz <john.stultz@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] staging: ion: chunk_heap: use %pad for printing dma_addr_t's

On Mon, May 04 2015 at 01:05:50 PM, Colin Cross <ccross@...roid.com> wrote:
> On Mon, May 4, 2015 at 1:22 AM, Dan Carpenter <dan.carpenter@...cle.com> wrote:
>> On Thu, Apr 09, 2015 at 06:10:04PM -0700, Mitchel Humpherys wrote:
>>> We're currently using %lu and %ld to print some variables of type
>>> dma_addr_t, which results in the following warning when dma_addr_t is
>>> 64-bits wide:
>>>
>>>     drivers/staging/android/ion/ion_chunk_heap.c: In function 'ion_chunk_heap_create':
>>>     drivers/staging/android/ion/ion_chunk_heap.c:176:2: warning: format '%lu' expects argument of type 'long unsigned int', but argument 3 has type 'dma_addr_t' [-Wformat=]
>>>       pr_info("%s: base %lu size %zu align %ld\n", __func__, chunk_heap->base,
>>>       ^
>>>     drivers/staging/android/ion/ion_chunk_heap.c:176:2: warning: format '%ld' expects argument of type 'long int', but argument 5 has type 'dma_addr_t' [-Wformat=]
>>>
>>> Fix this by using %pad as instructed in printk-formats.txt.
>>>
>>> Signed-off-by: Mitchel Humpherys <mitchelh@...eaurora.org>
>>
>> This one was just merged and I was about to email you that it introduces
>> some new Smatch warnings, but actually looking at it, it's just wrong.
>>
>> We want to print "chunk_heap->base" and not "&chunk_heap->base".
>
> This would be correct if base was a dma_addr_t...
>
>> And anyway "&chunk_heap->base" is a regular pointer, not a dma_addr_t.
>
> But it is actually an ion_phys_addr_t, which is currently typedef'd to
> unsigned long.  Are you using a local patch that replaces
> ion_phys_addr_t with dma_addr_t?
>
>> So please send a new patch that removes the &.
>
> Removing the & is not correct, lib/vsprintf.c will dereference the arg
> for %pad or %pap.  I think this patch should just be dropped, the old
> %lu was correct for what is in Linus' tree.

Ah, you're absolutely correct.  We have a local patch that makes
ion_phys_addr_t a dma_addr_t (needed for LPAE), which is why I needed to
convert the printk format...

Greg, can you please drop this patch from your tree?  We'll only need
this if/when mainline Ion gets LPAE support...


-Mitch

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